1. Field of the Invention
This invention relates to the disposal of animal waste, i.e., manure and is particularly concerned with a method of efficiently burning such waste material in a manner that is environmentally sound.
2. Prior Art
It has been estimated by the United States Department of Agriculture (USDA Report Misc. Pub. 1065, 1968) that nearly two billion tons of manure is generated annually in the United States. Using a density value of fifty pounds per cubic foot it has been calculated that this generated manure is enough to cover about thirty-five thousand square miles, i.e., the State of Indiana, with a one-inch layer annually. The problem is compounded by the fact that manure is produced in concentrated areas, such as feed lots, hog factories and large chicken factories, and in smaller animal processing operations, rather than being uniformly divided over the entire United States. Thus, large quantities need to be processed in local areas or both the large and small quantities need to be collected and transported to distant processing facilities.
Aside from the obvious odor problem associated with the processing of manure, other, not so obvious, problems exist. In many instances manure is mixed with water, as a result of the cleaning out of pens and stalls or by the falling rain and snow. The resulting contaminated water becomes a threat to streams, lakes and underground water supplies and ultimately to the drinking supply. Government agencies in areas of the United States having significant livestock operations are recognizing the dangers to the clean water supply and it has now become more difficult to obtain permits for large livestock operations in such areas. More recently it has become known that manure entering streams and lakes results in growth of organisms that attack and destroy fish in the streams and that even attack other animals and humans causing severe illness.
Even when used as fertilizer the animal wastes often present environmental problems that are costly and difficult to solve. For example, the manure generally contains weed seeds ingested by the animals with their feed grains. Present composting methods do not kill the weed seeds so herbicides are frequently added to the manure and when the manure is used as fertilizer the herbicide chemicals are added to the soil.
It is well recognized that when man creates environmental problems there is a cost associated with the clean-up or avoidance of the problem in the future. Trash dumped in the oceans, manufacturing process pollutants discharged into streams, rivers and lakes, exhaust emissions from automobiles and nuclear wastes are examples of environmental problems that are currently being addressed at great expense to the American taxpayer. Animal wastes represent just one more environmental problem that must be addressed to insure quality life for humans. Clearly, there is a need for methods and systems to dispose of manure, on-site, in a neat, cost effective manner.
At the present time current approaches to animal waste management are as old as the problem itself. Often it is merely spread on the ground as fertilizer or compost. Other times it is dumped into lagoons. Manure spread on the ground or placed in piles or in lagoons not only takes up large amounts of valuable ground space but creates incredible odors. The odors have resulted in the treating of the manure with chemicals to reduce or change the nature of the odors. The use of chemicals results in increased cost in the processing of the manure and the chemicals may not always be environmentally safe.
In most situations manure represents an expense and pollution liability rather than a marketable fertilizer product. In some instances, chicken litter (excreta and bedding material) can be used for cattle feed. In a limited number of areas manure is sold or given away. For most animal operations the manure is simply a nuisance. For producers unable to simply pile up manure there are, at the least, handling and transportation costs involved in moving the manure to a disposal location. Typically, for hogs, manure is produced approximately at the rate of two to three pounds per pound of weight gain. A hog will produce about six hundred pounds of manure over its four and one-half to six month life span. A producer marketing one thousand head per year would have about three hundred tons of raw manure to deal with. Since hog wastes are typically washed out of the hog pens, the total weight to be handled is probably three to four times the raw manure weight, or about one thousand tons. In addition to the costs involved in handling such large quantities of waste, it is noted that there are fewer and fewer locations where sites for the dumping of the large amount of waste can be handled. Consequently, the manure is confined to lagoons and becomes a nuisance to the producer and his neighbors.
There can be no doubt that there is a need for a method and system to dispose of manure, on-site, in a neat and cost effective manner.